The present invention relates to a taut band instrument and more particularly to a taut band instrument in which the balance of the moving portion including a moving coil therein is obtained very easily and a taut band hanging the moving portion is secured accurately and quickly to a holder member.
In general, a moving portion rotating a needle of an electric instrument is hung by a body member to indicate a measured value accurately. For the purpose of the above, the moving portion should be kept in balance horizontally and be positioned at its center.
In a conventional taut band instrument, the moving portion comprises a moving coil, a band plate, and boss members. The moving coil is wound on a frame which is made of aluminum and, furthermore, the moving coil with the frame is mounted on the boss member. The boss member includes a cylindrical projection which is loosenly inserted into a hole provided in a holder member. A taut band hanging the moving portion is fixed to the holder member at its end portion after passing through a passage provided in the cylindrical projection of the boss member. The boss member is usually made of phosophor bronze and the like and, when necessary, hide glue is added to an arm member which projects from the boss member in order to obtain weight balance for the moving portion. However, it is necessary to take much care for adjustment of the balance and, as a result, the construction of the boss member becomes complex.
Furthermore, in this construction, the taut band passes through the passage provided in the cylindrical projection. However, it is necessary to have much technical experience to fix the taut band accurately to the holder after being positioned at its center portion.
To overcome the above disadvantage, a pin member is applied to fix the taut band to the center portion in the boss member and a wedge is also adopted to fix the taut band to the center portion. However, according to this construction, the number of parts is increased and it is necessary to use a much more experienced technique to place the pin member. Furthermore, the wedge should be used to fixed the taut band onto the boss member so that workability is remarkably inefficient due to time consumption. Thus, it is necessary to take much care to assemble the parts and the process for making the instrument is complex.